<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            color:red;
            font-size: 18px;
        }
        .c1:hover{
            color: green;
            font-size: 50px;
        }
        .c2{
            height: 300px;
            width: 500px;
            border: 1px solid red;
        }
        .c2:hover{
            border: 3px solid green;
        }
        .download{
            display: none;
        }
        .app:hover .download{
            display: block;
        }
        .app:hover .title{
            color: red;
        }


        .c1:after{
            content: '大帅哥';
        }
        .area:after{
            content:"";
            display:block;
            clear:both;
        }
    </style>
</head>
<body>
    <div class="c1">联通</div>
    <div class="c2">广西</div>

    <div class="app">
        <div class="title">点我下载app</div>
        <div class="download">
            <a href="http://www.baidu.com">
                <img src="images/二维码.jpg" alt="">
            </a>

        </div>
    </div>
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</body>
</html>